Photochemical multicolor printing of textile and the like



United States Patent PHOTOCHEMICAL MULTICOLOR PRINTING OF TEXTILE AND THE LIKE Leonard E. Ravich, New York, N. Y., assignor to Brown- Allen Chemicals, Inc., New York, N. Y., a corporation of New York No Drawing. Application April 25, 1951, Serial No. 222,944

"14 Claims. (Cl. 956) This invention relates to multi-color printing of textiles and other web or sheet materials capable of being dyed or colored with diazo compounds and esters of leuco vat dye compounds. It has for its principal object the provision of an improved photo-chemical process for multi-color printing, and to provide a novel solution for use in carrying out the process, and a method for preparing the solution.

The printing process of the present invention makes use of the fact that dyes of the diazo type react differently to light radiation than dyes of the leuco ester type. Accordingly, before proceeding with a description of the invention, the uses of these two types of dyes will first be described, with particular reference to photo-chemical dyeing.

The application of the photo-sensitivity of diazo compounds has become a distinct part of photographic technology. Diazo emulsions can be used to make either positive or negative prints on textiles, paper, gelatin or other colloid films or metals, the pictures being fixed by coupling with a phenol or amine, the azo compound being substantially insoluble in water. The majority of diazo type processes use the destructive power of light to remove the diazo group in those areas which are irradiated or illuminated. Subsequentto irradiation, the undestroyed diazo-compound, that is, the diazocompound in the area which has not been irradiated, is fixed by coupling, and thus a positive is produced directly. The following is an example of a formula for use in applying a diazo print on sheet or web materials:

Nickel sulphate grams 5.6 Hydrochloric acid (conc.) cc 1.25 Tartaric acid ce 1.25 Sodium chloride gram-s 3.6 Urea do 30.0 Thiourea do 4.7 Uranium acetate solution (0.005%) cc 1.5 Aerosol OS "grams" 0.5 Stabilized diazonium salt do 3.5 1,2,4 acid do 0.1 Water to 2500 cc.

To the above solution is added 1 gram of b-naphthol dissolved in cc. ethyl alcohol.

The textile or other base material is coated or impregnated with this solution and exposed to a light source under a positive film or tracing. The material may be in either a wet or a dry condition when it is thus irradiated. In the normal diazo type processes, light of wave lengths in the blue or near ultra-violet is most effective in bringing about the decomposition of the diazonium salts. The diazonium compound is destroyed or decomposed by the light, and development is brought about by placing the base material in an alkaline medium. As a result, the undecomposed diazo compound couples with the beta-naphthol or coupling agent, and the image represented by the film or tracing is reproduced. The alkaline medium usually used in processes of this type is moist air, preferably warm, charged with ammonia.

The beta-naphthol coupling agent may, if desired, be omitted from the solution previously described. In this case, the base material to which the diazo solution has been applied is exposed to a source of radiation, after which the undestroyed or non-radiated portions of the diazonium salt are coupled to produce a colored image, by immersing the material in an alkaline solution of a coupler, such as beta-naphthol or Naphthol A. S. (anilide of 2,3-oxynaphthoic acid) or any of the other commonly used couplers known in the art.

Referring now to the use of dyes of the leuco ester type, stable and soluble derivatives of the leuco vat dyes are commonly produced by treating the sodium salts of the leuco base of the vat dye with chlorosulfonic acid. The resultant substance is the sodium salt of the sulfuric acid ester of the leuco vat dye. Dye substances of this type are commonly known by the trademarked term, Indigosols, and for convenience will thus be referred to throughout the remainder of the specification.

A base material is treated with the water solution of the Indigosol with or without the additions of materials to promote absorption or adhesion on or in the base. In the presence of oxygen and moisture, the sulfuric acid groups split off and the leuco derivative of the dye oxidizes to the original form of the dye, which is therefore precipitated on or in the base. The dyeings will oxidize in the air, although an oxidizing agent is frequently used to accelerate the precipitation. It is known that dried powdered Indigosols are somewhat sensitive to light, and when exposed to light for long periods the powder turns into the color of the original dye.

It is possible to produce a stable image on cloth or other sheet or web material at high speeds by the use of a sulfuric acid ester of a vat dyestuff along with a photosensitizer providing a light-energy absorption span much greater than that of the dyestuff or Indigosol. As disclosed in my co-pending application Serial No. 117,742, filed September 24, 1949, now abandoned, a uranyl salt, such as uranium acetate or uranium nitrate, may be used to particular advantage as the photo-sensitizer. When a solution of the Indigosol and the photo-sensitizer is applied to the base material and the latter is exposed to light radiatron in the ultra-violet range, the resulting photo-chemical reactions are essentially a saponification of the Indigosol to a leuco form of the vat dye and subsequent oxidation of the leuco form to the original vat color. In order for saponification to take place, irradiation must be effected in the presence of water. Since the molecular weight of the Indigosol of indigo is 500, while .that of water is 18, it is apparent that if the material were not completely dried there would be sufficient water present to provide the molecule needed for saponification to the leuco base form, which would then oxidize in air to form the dye. The

fompleted reaction would take place somewhat along these mes:

OSO3Na OSOQNa The above equation does not show the action of light. The photo-sensitizer serves to absorb and transform radiant energy from a wider hand than that to which the Indigosol is sensitive, into the energy of activation necessary for a rapid saponification reaction to occur. The effect of the sensitizer, therefore, is a physical rather than a chemical one, in that it supplies under the influence of light radiation in the visible spectrum a much greater energy of activation per unit time than is absorbed by the unsensitized Indigosol (sensitive mainly to the low wave lengths of light). In other words, there is absorption of radiated light energy by the uranyl salt and a formation of another energy level due to the fluorescent and other photo-chemical actions of the uranyl salt under the light radiation, and by reason of the greatly increased energy of activation made available by the sensitizer at the level to which the Indigosol is sensitive, the saponification reaction and oxidation, with resultant precipitation of the vat dye, occur very rapidly when a textile, paper or other base is coated or impregnated with the light-sensitive Indigosol and exposed to light radiation.

As an example of the technique of dyeing with a photosensitive Indigosol, a photo-sensitive solution may be repared consisting of the following: grams of the sodium salt of the lcuco compound of the dyestuff manufactured according to the German patent specification No. 430,558 from benzanthione and phthalic anhydride are dissolved in 800 cc. of water at l40-160 F. To this is added cc. of a 20% ammonium thiocyanate solution and 4 grams of a wetting agent, such as sodium lauryl sulfonate. The photo-sensitivity of the leuco ester to the upper portions of the spectrum is increased by adding to each liter of the above solution 1.5 cc. of a solution which, per gallon of water, consists of 1.35 grams of uranium acetate, 1.2 grams of uranine, 2.21 grams of eosine, 1.72 grams of cyanine and 1 gram of aerosol. The material to be dyed is coated or impregnated with the above solution and exposed to a source of radiant energy such as a rnercury vapor lamp emitting radiation between 2200 and 7500 angstrom units, for a time sufiicient to precipitate completely the vat dyestuff as a colored, light-fast and water-insolub1e material within the fiber. If the material is to be printed with a pattern or a photographic reproduction is to be made, the material, after application of the above-described solution thereto, is exposed to a strong actinic light source through a photo-plate or similar light screen on which there is reproduced the pattern or design to be applied to the base material. The portion of the base material which receives the light energy through the transparent portions of the photo-plate or screen contains the vat dye particles formed as previously described. The portion of the base material which has not been exposed to the light source contains the unchanged soluble sodium salt of the leuco ester of the vat dye. To fix the image on the base material so that it will be unaffected by further light exposure, it is necessary only to wash the base material to remove the photo-sensitive Indigosol solution from those portions not exposed to the light.

It will be apparent from the foregoing that in the use of the diazonium salt the colored portion of the base material finally appears at the area which was not exposed to light radiation, while in the use of the photosensitive Indigosol solution, the colored portion of the base material appears at the irradiated area.

According to the present invention, the diazonium salt and the Indigosol are applied in solution to the base material and exposed to light radiation over only part of the area of the material, and in the presence of water moisture, to decompose the diazonium salt on this irradiated part and precipitate the dye particles from the Indigosol on the irradiated part. Thereafter, the undecomposed diazonium salt, that is, the diazonium salt on the part which was not irradiated, is coupled to this last part of the material in the presence of an alkaline medium, and the Indigosol is washed or otherwise removed from the part to which the diazonium salt is coupled.

One way of practicing the invention is to apply the diazonium salt and the Indigosol to the base material by coating or impregnating the material with a solution of these two dyestuffs in a solvent, such as acetone, which is a solvent for both dyestuffs and is miscible with water. The solution also includes water, and the coupling agent for the diazonium salt is one which is soluble in the mixture of the water and the solvent for the diazonium salt and the Indigosol. The coupling agent, which may be beta naphthol or Naphthol A. 5., may be applied to the base material in solution after the irradiation. The diazonium salt solution and/ or the Indigosol solution preferably comprises also a photo'sensitizer, which may be a uranyl salt, such as uranium acetate or uranium nitrate, or a dye such as cyanine or thiocyanate. The uranyl salt or dye photo-sensitizer acts to accelerate the saponification of the Indigosol under the light radiation, so that the precipitation of the vat dye occurs at approximately the same speed as the decomposition of the diazonium salt under the light radiation.

Another way of practicing the invention is to apply the Indigosol solution to the base material by coating or impregnation, dry the material, then apply the diazonium salt and coupler, and then expose the material to light radiation and develop by exposure to moist air containing ammonia.

A further modification is applying the Indigosol solution by coating or impregnation, drying, applying the diazonium solution, exposing to radiation under a screen or negative plate, and then immersing the exposed material to an alkaline solution of the coupler.

Another modification is applying the diazonium salt plus the coupler and other addition agents to the base by coating or impregnation, drying, then applying the Indigosol solution, then exposing to radiation under a photo plate or screen, and developing the exposed base material by exposure to moist air containing the ammonia.

Still another modification is applying the diazonium solution to the base by coating or impregnation, then drying, applying the Indigosol solution, and exposing to radiation under a photo plate or screen. The exposed base is then immersed in an alkaline solution of the coupler.

Another modification is applying the Indigosol and coupler solution to the base material by coating or impregnation, drying, then applying the diazonium solution and exposing to radiation under a photo plate or screen, and developing by exposing to moist air containing ammonia.

In the above discussion the drying procedure between the application of the first and second solutions is not necessary for the invention to be operative, but the technique is helpful in that it facilitates absorption of the second solution.

EXAMPLE I To cc. of a filtered 8% solution of tetrabromw indigo in acetone are added 2 grams of the stabilized diazo compound of p-nitro-o-anisidine dissolved in 20 cc. of distilled water. To the above solution are added 70 cc. of an aqueous solution consisting of 20 grams of urea and 4 grams of thiourea along with 1.5 cc. of the previously described sensitizing solution containing uranium acetate. Then, 1 gram of beta-naphthol dis solved in 10 cc. of ethyl alcohol is added to the solution.

In preparing this solution, it is desirable that the acetone be present in an amount equal to at least 50% of the final solution, in order to prevent precipitation of the dyestufi in advance of the irradiation. It will be noted that while the beta-naphthol coupling agent is insoluble in water, it is soluble in the acetone-water mixture. I have found that if the acetone, water and alcohol are mixed together and then the solids of the abovewa ts described solution are added, precipitation will result prior to the irradiation, and consequently it is important to prepare the solution as above-described. By forming a solution of the acetone and the indigo, the non-solubles in the indigo can be filtered out.

The base material, which may be a textile fabric such as woven cotton, is impregnated or coated with the above-described solution and exposed to a source of radiant energy, such as that previously described, under a screen or negative containing the design which is to be reproduced. Under those portions of complete transparency on the negative or screen, the radiation causes the complete destruction of the diazonium compound and the complete saponification and oxidation of the tetrabromindigo to form a blue vat pigment color on the base material. Under those portions of the negative which are completely opaque, the diazonium salt remains unchanged and the tetrabromoindigo is not changed into the vat pigment. Upon subsequent exposure of the base material to an alkaline medium, such as warm moist air containing ammonia, the diazonium salt of p-nitro-oanisidine couples with the beta-naphthol present to form a red pigment color.

Under those portions of the negative which are partially transparent, a portion of the diazonium salt is destroyed and a portion of the tetrabromoindigo is converted to the vat pigment; and upon subsequent coupling with the beta-naphthol in an alkaline medium, as described above, a color is produced which is composed of blue and red. The degree of light transmission of the screen or negatives will determine the shade produced. All that is then necessary to fix the image permanently on the base material is to wash the material sufliciently in a mildly alkaline solution to remove the tetrabromoindigo not irradiated.

While I have referred to beta-naphthol as a coupling agent in the above example, other coupling agents may be used, provided that they are soluble in the acetonewater mixture. It will be understood that the coupling agent need not be applied to the base material in the above-described solution but may be applied to the material at any time as long as the material is not subjected to an alkaline medium until after the light-exposure. For example, the Indigosol and diazonium salt may be applied in solution to the base material, and then, subsequent to the irradiation, the base material may be immersed in an alkaline solution containing a suitable coupler, in which case the coupler does not need to be soluble in the acetone.

EXAMPLE II A base such as viscose rayon is impregnated with an 8% aqueous solution of tetrabromoindigo and with a photo-sensitizing solution which, per gallon of Water consists of 1.35 grams of uranium acetate, 1.2 grams of uranine, 2.21 grams of cosine, 1.72 grams of cyanine and 1 gram of aerosol. The base is then dried and subsequently coated with an aqueous solution containing 10 grams of the stabilized diazo compound of p-nitro-oanisidine per hundred cc. of water. The prepared base is then exposed to the source of light radiation in a moist state and subsequently immersed in an alkaline solution of Naphthol A. S.

EXAMPLE III The materials used are the same as in Example II, but the coupler is incorporated with the tetrabromoindigo, and development occurs after radiation by exposure to moist air containing ammonia.

EXAMPLE IV In this case the materials are the same as in Example II, but the diazonium salt is applied to the base, then dried and then the tetrabromoindigo is applied. Coupling here takes place by immersion in an alkaline solution of the coupler.

6 EXAMPLE v The materials are the same as in Example II, but the diazonium salt plus the coupler are applied to the base, which is then dried. The Indigosol is then applied in an aqueous solution and development takes place after irradiation by exposure to moist air containing ammonia.

Examples of other formulae which can be used in the above-described procedures are as follows:

The diazonium solution may comprise 25 grams of the stabilized diazo compound of diethyl-su1fonamido-oanisidine, 20 grams of diethylene glycol, and 1.5 cc. of the photo-sensitizing solution described in Example II, all dissolved in one liter of Water.

The Indigosol formula for this reaction can be 8 grams of tetrabromoindigo and 8 grams of Glyecine dissolved in cc. of water.

The coupler solution in which the impregnated base is immersed after irradiation is composed as follows:

20 grams of the anilide of 2,3-oxynaphthoic acid, 40 cc. of ethyl alcohol, 10 grams of sodium hydroxide, and 1 gram of Calgon, all dissolved in one liter of water.

The above 3 components are applied to the base material in whatever order is desired as described in the above examples.

The above solution will yield a print consisting of a blue color on a red background, or a red color on a blue background, or a color composed of various percentages of the red and blue. The type of print, its tones and the intensity of the colors are determined by the relative densities of the screen or photo-plate used between the source of radiation and the impregnated or coated base, which may be viscose rayon.

Formula 2 The diazo solution is 25 grams of the diazotized salt of 2,5-dichloroaniline, 20 grams of diethylene glycol, and 1.5 cc. of the photo-sensitizing solution described in Example II, all dissolved in one liter of water.

The coupler solution is composed of 10 grams of phloroglucinol, 20 grams of carboxylic acid, 40 cc. of ethyl alcohol, 10 grams of sodium hydroxide, and 1 gram of Calgon, all dissolved in one liter of Water.

The vat printing solution is composed of 8 grams of Indigosol Scarlet H. B. and 8 grams of Glyecine all dissolved in 100 cc. of water.

The above solution will result in a red image on a brown background, a brown image on a red background, or tones composed of various percentages of the brown and red. The colors are controlled by the relative densities of the photo-plate or the screen used.

It will be apparent from the above that the method will produce any two colors on a colorless base material, as well as an infinite variety of colors composed of varying proportions of the two primary colors.

I claim:

1. A process for multi-color printing of textiles and other base materials in sheet or Web form, which comprises applying a photosensitive diazonium salt and a photosensitized ester of a leuco vat dye compound in solution to an area of the base material, irradiating only part of said area in the presence of water to decompose the diazonium salt on said part and precipitate the dye particles from the leuco ester on said part, coupling the undecomposed diazonium salt in another part of said area in the presence of an azo dye coupling component and an alkaline medium, and removing the leuco ester from said last part.

2. A process according to claim 1, comprising also the step of applying to the base material a uranyl salt in solution as a photosensitizer, prior to said irradiation, whereby said precipitation is accelerated and takes place at approximately the same speed as said decomposition.

3. A process for multi-color printing of textiles and other base materials in sheet or web form, which comprises applying to an area of the base material a solution of a photosensitive diazonium salt and a photosensitive ester of a leuco vat dye compound in a solvent for both the salt and the leuco ester, said solvent being miscible with water, irradiating only part of said area in the presence of water to decompose the diazonium salt on said part and precipitate the dye particles from the leuco ester on said part, coupling the undecomposed diazonium salt in another part of said area in the presence of an azo dye coupling component and an alkaline medium, and removing the leuco ester from said last part.

4. A process according to claim 3, in which said solvent is acetone.

5. A process according to claim 3, in which the water is included in said solution.

6. A process according to claim 3, in which the water is included in said solution, the coupling being eifected with an azo dye coupling component which is soluble in the solvent-water mixture.

7. A process according to claim 3, in which said solution includes an azo dye coupling component for the diazonium salt.

8. A process according to claim 3, comprising also the step of applying to the base material, in said solution, a uranyl salt as a photosensitizer, whereby said precipitation is accelerated and takes place at approximately the same speed as said decomposition.

9. A process according to claim 3, in which said solvent constitutes at least 50% of said solution.

10. A solution for multi-color photochemical dyeing,

which comprises a diazonium salt, an ester of a leuco vat pound in a water-miscible solvent for both said salt and said leuco ester, and then adding to the aqueous solution an azo dye coupling component for said deazonium salt which is soluble in the mixture of water and solvent.

12. A method for preparing a solution for multi color photosensitive dyeing, which comprises forming an aqueous solution of a photo-sensitive diazonium salt and a photo-sensitive ester of a leuco vat dye compound in acetone, and then adding thereto beta-naphthol dissolved in alcohol.

13. A solution for multi-color photo-chemical dyeing consisting essentially of a photosensitive diazonium salt, a photo-sensitive ester of a leuco vat dye compound, water, a Water-miscible solvent for both said salt and said leuco ester, and an azo dye coupling component for the diazonium salt, said coupling component being soluble in the solvent-water solution.

14. The dyeing solution defined in claim 13 wherein said water-miscible solvent is acetone.

References Cited in the file of this patent UNITED STATES PATENTS 1,640,802 Petzold et a1. Aug. 30, 1927 1,678,580 Winterhalder July 24, 1928 1,724,109 Rath Aug. 13, 1929 1,738,530 Frankenburger et a1 Dec. 10, 1929 1,782,259 Eggert Nov. 18, 1930 1,876,052 Haendel Sept. 6, 1932 1,918,623 Wendt July 18, 1933 2,193,931 Michaelis Mar. 19, 1940 2,214,365 Flynn et al Sept. 10, 1940 2,375,366 Jacobus et a1. May 8, 1945 2,440,106 Land et al. Apr. 20, 1948 2,623,821 Isherwood et a1. Dec. 30, 1952 FOREIGN PATENTS 524,143 France May 7, 1921 417,588 Great Britain Oct. 4, 1934 

1. A PROCESS FOR MULTI-COLOR PRINTING OF TEXTILES AND OTHER BASE MATERIALS IN SHEET OR WEB FORM, WHICH COMPRISES APPLYING A PHOTOSENSITIVE DIAZONIUM SALT AND A PHOTOSENSITIZED ESTER OF A LEUCO VAT DYE COMPOUND IN SOLUTION TO AN AERA OF THE BASE MATERIAL, IRRADIATING ONLY PART OF SAID AREA IN THE PRESENCE OF WATER TO DECOMPOSE THE DIAZONIUM SALT ON SAID PART AND PRECIPITATE THE DYE PARTICLES FROM THE LEUCO ESTER ON SAID PART, COUPLING THE UNDERCOMPOSED DIAZONIUM SALT IN ANOTHER PART OF SAID AERA IN THE PRESENCE OF AN AZO DYE COUPLING COMPONENET AND AN ALKALINE MEDIUM AND REMOVING THE LEUCO ESTER FROM SAID LAST PART. 